1. Technical Field
The present invention relates generally to separating suspended phases from a liquid.
2. Description of Related Art
Many processes require clarification of a suspension (e.g., the removal of a suspended phase from a liquid). Some suspensions may be clarified using dissolved air flotation (DAF). Other dissolved gases (e.g., CH4) may also be used. Gases may be dissolved in a liquid at high pressures. Upon reduction in pressure (e.g., to atmospheric pressure), dissolved gases may precipitate out, and often precipitate as bubbles that rise through the liquid. Typically, rising gas bubbles interact with suspended particles (solids or liquids) and cause the particles to rise to the surface, creating a segregated layer of particles (often described as a mat) near the top, and a clarified liquid below.
Clarification using DAF may be challenging, particularly for small particles (e.g., below 100 microns), and/or particles that are neutrally buoyant or denser than the liquid. In some cases, clarification may be enhanced by flocculating the particles (forming “flocs” of particles). However, flocculation may require the addition of a flocculant to the suspension. Flocculants may contaminate downstream processes, create undesirable chemical reactions, be costly, and/or increase the energy intensity or greenhouse gas emissions of a process.
Some particles may form weak flocs. Reducing an amount of flocculant may also result in weak flocs. Weak flocs may be broken (i.e. deflocculated) by relatively small forces, such as forces associated with turbulence in the suspension. In some cases, large gas bubbles (e.g., over 500 microns) may deflocculate particles. Turbulence associated with various liquid injections, inlets, outlets, paddles, stirring, and the like may also deflocculate particles. Deflocculated particles may be more difficult to clarify. As such, preventing deflocculation (even for weakly flocculated suspensions) or providing the ability to clarify non-flocculated suspensions may improve certain processes.